1. Field of the Invention
The present invention relates to a novel flame retardative polycarbonate resin composition. More particularly, it pertains to a polycarbonate resin composition excellent in flame retardancy and capable of preventing dripping thereof at the time of combustion of a thin-walled material made from the composition highly fluidized while precluding the deterioration of the mechanical properties such as impact resistance as well as dimensional stability that are inherent in polycarbonate.
2. Description of Related Arts
A polycarbonate resin is excellent in mechanical strength, particularly impact strength, electrical properties, transparency and the like and is widely utilized in a variety of fields of office automation machinery, electric and electronic machinery, automobiles, architecture and the like. Some of the above-mentioned utilization fields typified by the fields of office automation machinery and electric and electronic machinery are required to have high flame retardancy.
Of various thermoplastic resins, polycarbonate has a high oxygen index and in general, a self-fire-extinguishing property. However, in order to meet the requirement on the safety in various application fields of office automation machinery, electric and electronic machinery and the like, there is strongly required the development of a resin composition which is further enhanced not only in flame retardancy but also in fluidity in view of the demand directed to thin-walled material.
A polycarbonate resin has heretofore been imparted with flame retardancy usually by being incorporated with a flame retardant and a flame retardant aid. The most prevailing flame retardant used for a polycarbonate is a bromine-based flame retardant.
However, the polycarbonate resin composition incorporated with such a bromine-based flame retardant involues the environmental problem that a gas generated at the time of combustion, for example, a gas generated at the time of combustion of the composition incorporated with decabromodiphenyl ether or the like causes a fear of containing dioxin which has been one of the most serious problems in recent years due to the influence on human bodies.
Such being the case, investigation on a nonbromine-based flame retardant is in progress for the sake of flame retardation of a polycarbonate resin. For example, Japanese Patent Publication No. 40445/1972 discloses a polycarbonate resin composition which is incorporated with an alkali metal salt or an alkaline earth metal salt of a perfluoroalkanesulfonic acid, but the technique disclosed therein suffers the disadvantage of causing dripping of the resin composition at the time combustion and thereby igniting the material immediately below it. Japanese Patent Publication No. 38419/1985 discloses a technique of preventing dripping of a polycarbonate resin at the time of combustion thereof by incorporating therein an alkali metal salt or an alkaline earth metal salt of a perfluoroalkanesulfonic acid and further adding a siloxane to the mixture. Nevertheless, the above-disclosed technique still suffers the drawback of causing dripping of the resin at the time of combustion and thereby igniting the material immediately below the resin in the case where the resin is highly fluized. In addition, Japanese Patent Publication No. 16473/1985 discloses a technique of preventing dripping of a polycarbonate resin at the time of combustion thereof by adding thereto an alkali metal salt of a perfluoroalkanesulfonic acid and a glass fiber, but the technique disclosed therein is not necessarily satisfactory.